Telecommunications systems with wireless telecommunications between mobile and/or stationary transceivers are special communication systems with a message transmission path between a message source and a message sink in which, for example, base stations and mobile parts are used as transceivers for message processing and transmission and in which
1) the message processing and message transmission can take place in one preferred direction of transmission (simplex mode) or in both directions of transmission (duplex mode),
2) the message processing is preferably digital,
3) the message transmission takes place wirelessly via the long-distance transmission link on the basis of various message transmission methods for multiple utilization of the message transmission link FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) and/or CDMA (Code Division Multiple Access)xe2x80x94e.g. according to radio standards such as DECT [Digital Enhanced (previously: European) Cordless Telecommunications; compare Nachrichtentechnik Elektronik 42 (1992) January/February No. 1, Berlin, DE; U. Pilger xe2x80x9cStruktur des DECT-Standardsxe2x80x9d [Structure of the DECT standard], pages 23 to 29 in conjunction with ETSI Publication ETS 300175-1 . . . 9, October 1992 and the DECT Publication of the DECT Forum, February 1997, pages 1 to 16], GSM [Groupe Speciale Mobile or Global System for Mobile Communication; compare Informatik Spektrum 14 (1991) June, No. 3, Berlin, DE; A. Mann: xe2x80x9cDer GSMxe2x80x94Standardxe2x80x94Grundlage fxc3xcr digitale europxc3xa4ische digital European mobile radio networks], pages 137 to 152 in conjunction with the publication telekom praxis April 1993, P. Smolka xe2x80x9cGSM-Funkschnittstellexe2x80x94Elemente und Funktionenxe2x80x9d, [GSM Radio Interfacexe2x80x94Elements and Functions], pages 17 to 24], UMTS [Universal Mobile Telecommunications System; compare (1): Nachrichtentechnik Elektronik, Berlin 45, 1995, vol. 1, pages 10 to 14 and vol. 2, pages 24 to 27; P. Jung, B. Steiner: xe2x80x9cKonzept eines CDMA-Mobilfunksystems mit gemeinsamer Detektion fxc3xcr die dritte Mobilfunkgenerationxe2x80x9d [Concept of a CDMA mobile radio system with joint detection for the third mobile radio generation]; (2): Nachrichtentechnik Elektronik, Berlin 41, 1991, vol. 6, pages 223 to 227 and page 234; P. W Baier, P. Jung, A. Klein: xe2x80x9cCDMAxe2x80x94ein gxc3xcnstiges Vielfachzugriffsverfahren fxc3xcr frequenzselektive und zeitvariante Mobilfunkkanxc3xa4lexe2x80x9d [CDMAxe2x80x94a favorable multiple access method for frequency-selective and time-variant mobile radio channels]; (3): IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E79-A, No. 12, December 1996, pages 1930 to 1937; P. W. Baier, P. Jung: xe2x80x9cCDMA Myths and Realities Revisitedxe2x80x9d; (4): IEEE Personal Communications, February 1995, pages 38 to 47; A. Urie, M Streeton, C Mourot: xe2x80x9cAn Advanced TDMA Mobile Access System for UMTSxe2x80x9d; (5): telekom praxis, May 1995, pages 9 to 14; P. W. Baier: xe2x80x9cSpread-Spectrum-Technik und CDMAxe2x80x94eine ursprxc3xcglich militxc3xa4rische Technik erobert den zivilen Bereichxe2x80x9d [Spread Spectrum Technology and CDMAxe2x80x94a technology of military origin conquers the civil domain]; (6): IEEE Personal Communications, February 1995, pages 48 to 53; P. G. Andermo, L. M. Ewerbring: xe2x80x9cAn CDMA-Based Radio Access Design for UMTSxe2x80x9d; (7): ITG Pachberichte 124 (1993), Berlin, Offenbach: VDE Verlag ISBN 3-8007-1965-7, pages 67 to 75; Dr. T. Zimmermann, Siemens AG: xe2x80x9cAnwendung von CDMA in der Mobilkommunikationxe2x80x9d [Applying CDMA in mobile communications]; (8): telecom report 16, (1993), vol. 1, pages 38 to 41; Dr. T. Ketseoglou, Siemens AG and Dr. T. Zimmermann, Siemens AG: xe2x80x9cEffizienter Teilnehmerzugriff fxc3xcr die 3. Generation der Mobilkommunikationxe2x80x94Vielfachzugriffsverfahren CDMA macht Luftschnittstelle flexiblerxe2x80x9d [efficient subscriber access for the 3rd generation of mobile communicationsxe2x80x94the multiple access method CDMA makes the air interface more flexible]; (9): Funkschau June 1998: R. Sietmann xe2x80x9cRingen um die UMTS-Schnittstellexe2x80x9d [The struggling for the UMTS interface], pages 76 to 81] WACS or PACS, IS-54, IS-95, PHS, PDC etc. [compare IEEE Communications Magazine, January 1995, pages 50 to 57; D. D. Falconer et al: xe2x80x9cTime Division Multiple Access Methods for Wireless Personal Communicationsxe2x80x9d].
xe2x80x9cMessagexe2x80x9d is a generic term which stands both for the meaning (information) and for the physical representation (signal). Even if a message has the same meaningxe2x80x94i.e. the same informationxe2x80x94different signal forms can occur. Thus, for example, a message concerning an object can be transmitted
(1) in the form of an image,
(2) as spoken word,
(3) as written word,
(4) as encrypted word or image.
The type of transmission according to (1) . . . (3) is here normally characterized by continuous (analog) signals, whereas the type of transmission according to (4) normally produces discontinuous signals (e.g. pulses, digital signals).
It is of great importance to carry out a power control for the telecommunications systems specified above, and especially for the CDMA-based telecommunications systems, because of the xe2x80x9cnear-farxe2x80x9d (compare: (10) K. D. Kammeyer xe2x80x9cNachrichtenxc3xcbertragungxe2x80x9d [Message Transmission], B. G. Teubner Stuttgart 1996, chapter 16.1.3, especially page 636; (11) K. David/T. Benkner xe2x80x9cDigitale Mobilfunksystemexe2x80x9d [Digital Mobile Radio Systems], B. G. Teubner Stuttgart 1996, chapter 8.7.2.2, especially page 414).
Power control is known as a means for reducing interference in multicellular mobile radio networks. The basic idea is to allocate to each subscriber only the amount of transmitting power currently needed by him for achieving the desired quality of service. This measure clearly reduces the interference with respect to other subscribers in the same or adjacent cells. However, this technique can only be applied to so-called xe2x80x9cpoint-to-pointxe2x80x9d connections in cellular mobile radio since, in this case, the transmitting powers to be used for the transmission, e.g. between stationary and mobile transceivers, that is from a base station or fixed part to the mobile station or mobile part and vice versa, can be explicitly dedicated to the link between the base station and mobile station.
In mobile radio telecommunications systems (e.g. GSM, UMTS) which operate preferably in licensed coordinated system operation, and in cordless telecommunications systems (e.g. DECT, PHS etc.) which preferably operate in unlicensed uncoordinated system operation, however, point-to-multipoint connections are also used. Channels using such links are generally Control Channels, the so-called xe2x80x9cCommon Control Channels (CCCH)xe2x80x9d. The most important representative of this category is, without any doubt, the so-called xe2x80x9cBroadcast Control Channel (BCCH)xe2x80x9d. It is radiated in the down link (DL) by the base station. The broadcast control channel has the task of transporting cell-related information and synchronization information. These information items are used by all mobile stations located within the cell. Since, however, the positions of the mobile stations within the radio cell and thus also the transmitting powers needed can differ greatly, it is not possible to control the transmitting power of the broadcast control channel in cellular mobile radio. As a rule, the transmitting power of the broadcast control channel is adapted in such a manner that it can still be received with adequate power by all mobile stations at the edge of the cell.
Power control is not used either for the xe2x80x9ctraffic channel (TCH)xe2x80x9d or for the xe2x80x9cbroadcast control channelxe2x80x9d in the previous cordless telecommunications systems (e.g. DECT).
The object forming the basis of the invention consists in controlling the transmitting power provided for point-to-multipoint telecommunications links in a telecommunications system with wireless telecommunications and uncoordinated unlicensed system operationxe2x80x94especially in a universal mobile telecommunications system with uncoordinated unlicensed system operation and a coordinated licensed system operation, without significant restriction of the transmitting range.
This object is achieved by a method for controlling power in point-to-multipoint telecommunications links in telecommunications systems with wireless telecommunications and uncoordinated unlicensed system operation, comprising the following features: (a) a SCHEDULED number of mobile parts registered in the base station is allocated to the coverage area of a base station supporting uncoordinated unlicensed system operation, (b) the base station sends a first message to the mobile parts located within the coverage area of the base station at a predetermined first time recurring at regular intervals in connection with a point-to-multipoint telecommunications link, (c) the respective mobile part sends a second message to the base station in each case at a mobile-part-specific second time recurring at regular intervals, the second time being determinable by events, such as especially the entry of the mobile part into the coverage area, the exit of the mobile part from the coverage area and/or the request for setting up a point-to-point telecommunications link by the mobile part, (d) the base station detects, by means of the second messages sent by the mobile parts, an ACTUAL number of mobile parts registered in the base station and located within the coverage area of the base station, (e) if the ACTUAL number matches the SCHEDULED number, the base station sends the first message with a first transmitting power which is reduced compared with a maximum power and which is dimensioned in such a manner that a mobile part, the second message of which has been received as the weakest one in the base station, still reliably receives the first message, (f) if the ACTUAL number does not match the SCHEDULED number, the base station alternately sends the first message with the maximum transmitting power for a predetermined first period of time and then with the first transmitting power for a predetermined second period of time.
The concept, proposed above, for the power control of point-to-multipoint telecommunications linksxe2x80x94especially of the broadcast control channelxe2x80x94for telecommunications systems with wireless telecommunications and uncoordinated unlicensed system operationxe2x80x94especially future cordless telecommunications systems such as xe2x80x9cresidential UMTSxe2x80x9d systemsxe2x80x94makes use of the fact that the maximum number of mobile stations registered in a base station is known. Thus, the base station knows at any time how many and which mobile stations are registered. If all mobile stations are registeredxe2x80x94i.e. if a SCHEDULED number of mobile stations registered in the base station corresponds to an ACTUAL number of mobile stations registered in the base station (NACT=NSCHED)xe2x80x94, the base station can match the transmitting power (first transmitting power) to the mobile station received as the xe2x80x9cweakest onexe2x80x9d. In other cases, if not all mobile stations are registeredxe2x80x94i.e. if the SCHEDULED number of mobile stations registered in the base station does not correspond to the ACTUAL number of mobile stations registered in the base station (NACTxe2x89xa0NSCHED)xe2x80x94, the base station will alternately transmit with the maximum transmitting power for a predetermined first period of time and then with the reduced transmitting power, which matches the mobile station received as the xe2x80x9cweakest onexe2x80x9d, for a predetermined second period of time. This provides for an optimum (dynamic) matching of the transmitting power to the continuously varying number of mobile stations located within the coverage area of the base station.
This procedure described above is possible because, as a rule, one mobile station will be operated for each base station and this is also registered, as a rule, in cordless telecommunications systems. The transmitting power selected by the base station in the first-mentioned case (all mobile stations are registered) will essentially be reduced compared with the maximum transmitting power (in the clearly predominant number of cases). The power-controlled point-to-multipoint telecommunications link minimizes the interference with other cordless telecommunications systems and thus improves the capability of coexistence. The method described above is suitable both for TDMA/FDMA-based systems and for CDMA-based systems. Power control is essential especially for CDMA-based systems since this makes it possible to considerably reduce the xe2x80x9cnear-farxe2x80x9d problem.
According to a preferred embodiment, it is advantageous if the second period of time, according to a limit value consideration for periods of time, on the assumption, which is generally valid for this, that a period of time can have a positive value between xe2x80x9czeroxe2x80x9d andxe2x80x94viewed theoreticallyxe2x80x94xe2x80x9carbitrary or infinitexe2x80x9d, has the value xe2x80x9czeroxe2x80x9d, that is to say the base station only transmits with maximum transmitting power if the ACTUAL number does not match the SCHEDULED number, the base station alternately sends the first message with the maximum transmitting power for a predetermined first period of time and then with the first transmitting power for a predetermined second period of time.
Additional advantageous further developments of the invention are provided in that the point-to-multipoint telecommunications link is used for a broadcast control channel. The wireless telecommunications is carried out in accordance with the CDMA, FDMA, and/or TDMA access method and in accordance with the TDD and/or FDD principle.